Effect of eardrum perforation and chronic otitis media on the results of infrared tympanic thermometer in adults: A systematic review and meta-analysis

Background: This study was conducted to determine whether tympanic membrane perforation or chronic otitis media affects the results of an infrared tympanic membrane thermometer in adults. Methods: A literature search was performed using PubMed, Embase, Cochrane Library, Web of Science, and Google Scholar. Results: Four nonrandomized studies were included in the analysis. The temperatures of the bilateral eardrums (one eardrum with normal condition [control group] and the other eardrum with perforation or chronic otitis media [experimental group]) were measured for the same subject in the studies. The mean and standard deviation of the bilateral tympanic membrane temperatures were used to calculate the mean difference (MD) with a corresponding 95% confidence interval (CI). The fixed-effect model was utilized based on the results of the heterogeneity measurement using the Chi2 test and I2 statistic. The results of a meta-analysis in the normal eardrum (control group) and perforated eardrum, chronic suppurative otitis media with tympanic membrane perforation, or chronic otitis media with cholesteatoma (experimental group) were 343 subjects (MD = 0.05; 95% CI = −0.00 to 0.11; P = .06). A meta-analysis of the normal eardrum (control group) and perforated eardrum or chronic suppurative otitis media with tympanic membrane perforation except for cholesteatoma (experimental group) found 296 subjects (MD = 0.05; 95% CI = −0.01 to 0.11; P = .10). Conclusion: When the temperatures of the bilateral eardrums were measured using an infrared tympanic membrane thermometer, no difference was observed between the eardrum with perforation or chronic otitis media and the normal eardrum.


Introduction
One of the critical information that reflects the patient's physical condition is body temperature.Due to the Coronavirus disease 2019 (COVID-19) pandemic, body temperature measurement is recognized as more important than ever before, not only in the medical field but also in daily life.An infrared tympanic membrane thermometer (ITMT) measures the radiant heat emitted from the eardrum; such heat is considered as the body temperature.This device requires a short testing time and provides relatively highly accurate results.[3][4][5] However, when the temperature is measured using an ITMT, the eardrum condition is not checked and is assumed to be normal.This study aimed to determine whether tympanic membrane perforation affects eardrum temperature measured using ITMT through a systematic review and meta-analysis.Suppose that eardrum perforation affects the result of the ITMT measurement, the ear thermometer reading, which is considered the body temperature, may be higher or lower than the actual value when the eardrum is perforated.As this can lead to errors in the assessment of the patient's physical condition, it is crucial to determine whether a difference exists in the temperatures between a normal and a perforated eardrum.

Search strategy
Systematic literature review and meta-analysis were conducted according to the Preferred Reporting Items for Systemic Review and Meta-analyses guidelines. [6]A literature search was performed using PubMed, Embase, Cochrane Library, Web of Science, and Google Scholar from the date of inception to February 06, 2023.The search terms are presented in the supplemental content (see Table S1, Supplemental Digital Content, http://links.lww.com/MD/K553, which shows the search strategy and result in each database), and the language was restricted to English.

Inclusion and exclusion criteria
Studies that compared the subjects' bilateral eardrum temperatures measured using an ITMT for adults were included.Thus, all subjects had 1 normal eardrum and 1 with perforation or chronic otitis media.Studies that involved subjects with acute otitis media, otitis media with effusion, or eardrums with inserted ventilation tubes were excluded, as well as studies that included children or animals.

Data extraction and quality assessment
The primary outcome of this study was the difference in the temperatures between a normal eardrum and an eardrum with perforation or chronic otitis media measured using the ITMT.
In other words, the control group was the temperature of the normal eardrum, and the experimental group was the temperature of the opposite eardrum with perforation of the same subject.The difference in the temperatures between the bilateral eardrums was analyzed using the averages and standard deviations of both groups.
The 3 authors of this study independently reviewed each of the included studies.They extracted data on the first author's name, year of publication, study location, study design, condition of the subjects' eardrums, number and age of the subjects, and mean and standard deviation of the eardrum temperatures.In the case of inconsistent data, the reviewers resolved them through a discussion.
The patients included in the study by Kim (2022) had chronic suppurative otitis media (CSOM) with tympanic membrane perforation (n = 145) or chronic otitis media with cholesteatoma (n = 47). [7]The patients' tympanic membrane temperatures were measured the day before surgery.10] Because Kim (2022) is one (Kim YH) of the authors of this study, analysis using bilateral tympanic membrane temperature results on the day before surgery for only patients with CSOM with tympanic membrane perforation could be separately implemented, excluding patients with chronic otitis media with cholesteatoma, which are the unpublished data of Kim (2022).
Among the data of Kim (2022), the published data (CSOM with tympanic membrane perforation and chronic otitis media with cholesteatoma) were summarized as Data (A) and the unpublished data (only CSOM with tympanic membrane perforation except for chronic otitis media with cholesteatoma) as Data (B).
The Risk of Bias Assessment Tool for Nonrandomized Studies (RoBANS) was used for the quality assessment of nonrandomized studies. [11]

Statistical analyses
To determine the effect of tympanic membrane perforation on the ITMT measurements, the temperature readings (mean ± standard deviation) in the normal and perforated eardrums were compared.Statistical analysis was conducted using Cochrane Review Manager (RevMan, version 5.4.1).The mean difference (MD) was calculated with 95% confidence intervals (CIs) for outcomes measured on a continuous scale.P < .05 was considered to indicate statistical significance.P < .1 in the Chi 2 test or I 2 > 50% in the I 2 statistic was considered to denote statistically significant heterogeneity, and a random-effects model would be used, otherwise, a fixed-effects model.

Ethical consideration
Generally, a systematic review and a meta-analysis are exempt from Institutional Review Board screening due to the use of published data and noninclusion of individualized patient data.However, because this study included unpublished data from Kim (2022), approval from the Institutional Review Board was obtained (CR-23-034).

Systematic literature review
9][10] The selection process for the studies to be included is presented in Figure 1.

Characteristics of the studies and quality assessment
Details of the 4 included studies and bilateral eardrum temperatures (control group, normal eardrum; experimental group, tympanic membrane contralateral to the normal eardrum in the same subjects) are presented in Table 1.The total number of subjects included in the 4 studies was 343.][10] The RoBANS, which consisted of 6 domains, was used to assess the risk of bias in the included studies, and the results are presented in Table 2.Each domain of the RoBANS was evaluated according to the criteria for judgment in the Appendix section of the article. [11]In the evaluation, the same results were obtained for all the included studies."Selection of participants" was considered to be of low risk because the eardrum temperature was measured by separating both ears into a control group and an experimental group on the same subject.In the analysis, comparisons were made without stratification or statistical adjustment; thus, "Confounding variables" were considered to be of high risk.Because they included prospective or retrospective studies using tympanic temperature and findings in the tympanic membrane obtained from medical records, "Measurement of exposure" was considered to be of low risk.Although blinding was not performed, "Blinding of outcome assessments" could also be considered to be of low risk as blinding did not affect the temperature objectively measured using an ITMT.Because the data used for the analysis of the results were found to have no missing data, "Incomplete outcome data" was also considered to be of low risk.Furthermore, because primary outcomes were planned and analyzed in the research protocol, "Selective outcome reporting" was considered to be of low risk.

Outcomes
The results of the 4 studies were analyzed for the difference in the temperatures between the normal and the perforated eardrums.In all these studies, the temperature of the tympanic membrane with perforation or chronic otitis media was higher than that of the normal eardrum.However, no statistically significant difference was observed in the fixed-effects model of the present study (Fig. 2).
Both analysis results indicated that there was no difference in the temperatures between the normal eardrum and the eardrum with tympanic membrane with perforation or chronic otitis media.

Sensitivity analysis and publication bias
In each analysis, which included Data (A) and Data (B) of Kim (2022), all of both P = .96on the Chi 2 test and I 2 = 0% on the I 2 statistic.Thus, a fixed-effects model was used in both analyses as significant heterogeneity was not observed among the studies (Fig. 2).Furthermore, a funnel plot was used to confirm publication bias.Although the number of studies included in the analysis was too small to analyze publication bias, it seemed that no apparent bias existed (Fig. 3).

Discussion
Chronic otitis media includes cases associated with middle ear cholesteatoma and CSOM with tympanic membrane perforation but no cholesteatoma.Kim (2022) presented the analysis results using eardrum temperatures measured the day before surgery in patients with chronic otitis media (CSOM with tympanic membrane perforation and chronic otitis media with cholesteatoma). [7]he eardrum condition of the subjects in the studies by Schmal  (2006) and Tasli (2018) was described as monaural central perforation of the tympanic membrane without signs of infection. [8,9]"No signs of infection" can be interpreted as the absence of acute infection, which means there is no ear discharge.That is, the eardrum in the experimental group had dry perforation.Furthermore, the otologic condition of the subjects in the study by Cengiz (2021) was described as monaural dry perforation without drainage for the preceding 3 months and normal middle ear mucosa. [10]The eardrum perforations were caused by chronic otitis media without cholesteatoma.It is necessary to note "CSOM with tympanic membrane perforation" among the subjects in the study by Kim (2022).The disease is usually operated on when the period without ear discharge lasts for at least 3 to 4 weeks. [12]n other words, the tympanic membranes of the subjects had dry perforation during the temperature measurement.Because the tympanic membrane temperature was measured on the day before surgery, it can be assumed that the subjects' eardrum condition was almost the same as that of the subjects included in the studies by Schmal (2006), Tasli (2018), and Cengiz (2021).
The experimental groups in the studies by Schmal (2006) and Tasli (2018) had perforation, the cause of which was not described.The most frequent cause of tympanic membrane perforation is chronic otitis media; another cause is trauma. [13,14]ven if tympanic membrane perforation is caused by other than chronic otitis media, while the perforation of the eardrum persists, chronic otitis media is more likely to be accompanied.This may be because the perforated eardrum causes the exposed mucosa of the middle ear cavity to become vulnerable to infection more than the normal eardrum.Therefore, it is very likely that most of the subjects included in the studies by Schmal (2006) and Tasli (2018) had eardrum perforation (eardrum perforation caused by chronic otitis media or accompanying chronic otitis media after eardrum perforation) associated with chronic otitis media.In summary, the analysis using Data (A) of Kim (2022) is close to the result of the effect of chronic otitis media on temperature measurement using ITMT; the result of the analysis using Data (B) of Kim (2022) can be considered as a result of analyzing the effect of the perforated eardrum on temperature measurement using ITMT.The ITMT measures the radiant emitted from the tympanic membrane. [15,16]If the eardrum is perforated, it can be considered that the infrared radiation released from not only the eardrum but also the mucosal membrane of the middle ear cavity can be detected by the ITMT sensor.This study aimed to determine whether such a situation affects the temperature measurement using ITMT through a systematic review and meta-analysis.When the results of individual studies published so far, Schmal (2006), Tasli (2018), and Cengiz (2021), no statistically significant difference was observed in the temperatures between the normal and perforated eardrums; on the other hand, Data (A) and Data (B) of Kim (2022) indicated statistically significant differences.Therefore, the statistical analyses of the individual studies did not reveal consistent results.17][18] Considering that the middle ear cavity receives the same arterial blood supply from the carotid artery as the tympanic membrane, [18] it can be inferred that no difference exists in the temperatures between the perforated and the normal eardrums.However, because the distance from the exposed mucosa of the middle ear cavity to the ITMT sensor is greater than that from the eardrum to it, the temperature of the perforated eardrum could be expected to be lower than that of the normal eardrum.Conversely, because the mucosa of the middle ear cavity is located more internally than the eardrum and is less affected by outside temperature, the ITMT readings could be expected to be higher in the perforated eardrum than in the normal eardrum.In this study, no difference was observed in the temperatures between the eardrum with perforation or chronic otitis media and the normal eardrum measured using ITMT.

Conclusion
A meta-analysis was conducted using data from 4 nonrandomized studies.It was found that tympanic membrane perforation or chronic otitis media without acute inflammation did not affect the temperature measurement using ITMT in adults.

Figure 1 .
Figure 1.Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) flow diagram of the study selection process.

Table 1
Patient characteristics and summarized data of the included studies.